This invention relates to a mixing method of synthesizing a compound by reacting at least two components.
In a light-sensitive material, various compounds have been used. For example, active methylene compounds represented by acetoacetic acid ester, acetoacetic anilide, malonic acid ester and dimedone are compounds useful as an intermediate of a compound used for a photographic light-sensitive material. Further, these compounds have been used as an intermediate of an agricultural chemical, a medicine, a dye or a pigment. Also, halides of these compounds are important compounds. The active methylene compounds can be easily halogenated by reacting with a halogenating reagent such as chlorine, bromine, sulfuryl chloride or N-chlorosuccinimide.
When sulfuryl chloride is used as a halogenating reagent, as a solvent for the active methylene chloride, there may be mainly used a halogen type solvent such as chloroform, carbon tetrachloride, methylene chloride, dichloroethane, trichloroethane or tetrachloroethane.
However, there is a fear of influence of this kind of the halogen type solvent on human bodies so that it has been proposed to use a solvent other than a halogen type solvent as described in Japanese Provisional Patent Publication No. 230638/1992.
As described in Example 1 of Japanese Provisional Patent Publication No. 230638/1992, when the active methylene compound is batchwisely halogenated with a halogenating reagent (sulfuryl chloride) by mixing both of them in a vessel by using a stirrer, for example, a 2,2-dichloro compound is formed as a by-product. Further, when ethyl acetate is used as a solvent in place of the halogen type solvent as shown in Example 1 of the above publication, a generation amount of the above by-product is the same level in small scale production, but said amount is larger in large scale production, as compared with the case of using the halogen type solvent. As a result, lowering in yield of a desired halide of the active methylene compound is brought about, and also lowering in quality is brought about. The by-product has the same chemical structure as that of the desired compound so that it is difficult to separate the by-product in subsequent steps. Therefore, as to a photographic starting compound high quality of which is absolutely required, it has been demanded to reduce an amount of a by-product as far as possible. The reaction rate of the above halogenation is as extremely rapid as 10 minutes or shorter in terms of a half-life thereof.
The cause for generating the by-product during synthesis is considered that when the desired compound is synthesized by chlorinating the active methylene compound with sulfuryl chloride, the desired compound formed and sulfuryl chloride exist locally with high concentrations so that a reaction from the desired compound to the by-product proceeds easily. When the reaction is carried out in a reaction system in which a solvent is used in a smaller amount and the active methylene compound is used with high concentration in order to obtain high productivity, a reaction mixture has an increased viscosity, and as a result, diffusion is inhibited so that the desired compound and sulfuryl chloride exist locally with high concentrations, whereby a reaction of the desired compound and sulfuryl chloride is accelerated to generate the by-product more easily.
In order to effect sufficient diffusion in a reaction system, it is necessary to increase the rotary number of a stirrer to carry out stirring sufficiently. As to increase in the rotary number of a stirrer, there is a mechanical limit, and also a necessary amount of energy is increased.
In order to solve the above problems, the present inventors have proposed to carry out a reaction while mixing a first reaction solution and a second reaction solution successively by using a static mixing device in Japanese Provisional Patent Publication No. 249583/1993.
By the above reaction method, generation of a by-product can be suppressed and a production cost can be decreased. However, it is necessary to control a flow rate precisely so that an equipment cost is large and there is a limit in decreasing the production cost. Further, the by-product exerts great influence on quality of the desired compound so that in order to further improve said quality, it has been demanded to reduce an amount the by-product by 0.1% order.